Robobot mission

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Robobot mission software

This figure shows the mission functional blocks. The main connection is to the robobot_bridge, through which the robot is controlled. The red mission block is the main block, where the behaviour is controlled. To help decide and control the behaviour, there is a number of data elements available in the bottom row of boxes, available through the bridge. A camera block is available, where image processing is assumed to happen. From the camera block, there is support for ArUco marker detection.

The blocks marked with a circle arrow is running their own thread. The yellow boxes are features available outside the mission application.

The mission application executable is in /home/local/mission/build:

local@solvej:~ $ cd mission/build
local@solvej:~/mission/build $ ./mission
image size 960x1280
Connecting to camera
Connected to pi-camera ='00000000a0604732
# Welcome to REGBOT bridge - send 'help' for more info
# press green to start.
Press h for help (q for quit)
>> 

When the application is starting it opens the camera and displays the used image size (960x1280) and the camera serial number 00000000a0604732. Then it connects to the bridge, that reply "# Welcome to REGBOT bridge". The connection to the bridge is strictly needed, otherwise the mission app terminates.

The "# press green to start." is information from the actual mission plan.

There is a prompt at the end ">>" indication that the keyboard is active.

Main

When the mission app is started a number of functions are available from the keyboard.

Press h (and enter) to get a list of features:

>> h
# got 'h' n=1
# mission command options
#    a    Do an ArUco analysis of a frame (no debug - faster)
#    b    Bridge restart
#    c    Capture an image and save to disk (image*.png)
#    d 1/0 Set/clear flag to save ArUco debug images, is=0
#    h    This help
#    lo xxx  Open log for xxx (pose 0, hbt 0, bridge 0, imu 0
#               ir 0, motor 0, joy 0, event 0, cam 0, aruco 0, mission 0)
#    lc xxx  Close log for xxx
#    o    Loop-test for steady ArUco marker (makes logfile)
#    p 99 Camera pan (Yaw) degrees (positive CCV) is 0.0 deg
#    q    Quit now
#    r 99 Camera roll degrees (positive left), is 0.0 deg
#    s    Status (all)
#    t 99 Camera tilt degrees (positive down), is 10.0 deg
#    2 x y h d    To face destination (x,y,h) at dist d 
#    3 x y h      Camera position on robot (is 0.030, 0.030, 0.270) [m]
#
# NB!  Robot may continue to move if this app is stopped with ctrl-C.
>> 

Log-files can be opened, this is a nice feature for debugging and analyzing sensor behaviour. e.g. the command

>> lo pose hbt imu ir motor joy event cam aruco mission

will open logfiles for most of the available data - except the bridge, that logs all communication.

The camera pose should be set in "ucamera.h", but can temporarily be changed here with the 'p', 'r', 't' and '3' commands.

The status list 's' gives an actual status for rather many data points, including 'data age', the time since the last update.

In the line starting with '3' is shown current camera position on the robot, relative to the centre between the driving wheels at floor level 3cm more forward, 3cm to the left and 27cm above the ground.

Logfiles

The data blocks have a data logger feature that can be enabled and disabled. The interface logfile will be in a text format for MATLAB import. The name of the log-file will include date and time, and will therefore not overwrite the previous logfile.

The IR logfile could be named 'log_irdist_20200105_133333.297.txt' look like this:

% robobot mission IR distance log
% 1 Timestamp in seconds
% 2 IR 1 distance [meter]
% 3 IR 2 distance [meter]
% 4 IR 1 raw [AD value]
% 5 IR 2 raw [AD value]
1578227613.337 0.250 0.730 33549 5864
1578227613.372 0.249 0.740 33649 5687
1578227613.419 0.250 0.759 33476 5330
1578227613.455 0.250 0.716 33468 6147
1578227613.494 0.250 0.727 33470 5936

And can be displayed in MATLAB using a script like this

ir = load('log_irdist_20200105_133333.297.txt'); % 
h = figure(300)
hold off
plot(ir(:,1) - ir(1,1), ir(:,2));
hold on
plot(ir(:,1) - ir(1,1), ir(:,3));
grid on
grid MINOR
axis([5,12,0,1])
legend('IR 1 distance', 'IR 2 distance','location','southwest')
xlabel('sec')
ylabel('distance [m]')
saveas(h, 'ir1-ir2.png')

And in this case, the plot shows:

The plot shows that longer distances (IR2) have more noise than shorter distances (IR1). In this case the drive is started by an IR2 distance less than 0.3m (at 6 seconds), hereafter the robot moves and the IR 1 distance (looking right) sees different obstacles.

Bridge

This part handles the interface with the regbot_bridge application. This two-way communication handles each direction individually.

Sending messages is mostly handled by the mission block, here regular updates of data is requested for the data blocks - e.g. robot pose, joystick buttons, IR-sensor measurements etc.

The receiving part of the bridge is always waiting for messages and distribute them for the relevant data block for decoding.

In a normal setup, about 150 messages will be received each second.

Data elements

This is a list of the features of each of the data elements.

IMU

The IMU is an MPU-9150 chip from InvenSense, that provide accelerometer and gyro signals on all 3 axes.

Accelerometer data. The z-axis shows the gravity acceleration, and when the robot starts driving after 6 seconds, there is clearly some bumping, that is seen as noise. The robot holds a pause at about 10 to 10.5 seconds and then turns a bit. The values on the x-axis (forward) ought to show some lateral acceleration, but it is hard to see in the noise.

Gyro data. While driving forward (from 6 to 10 seconds) there is a significant amount of noise. The robot holds a pause at about 10 to 10.5 seconds and then turns a bit. The turning (from 10.5 to 11.5 seconds) is clearly visible on the gyro z-axes.

The data is accessible in the mission code as:

bridge->imu->acc[0]   Acceleration in x-axes (forward) [m/s^2]
bridge->imu->acc[1]   y-axis (left)
bridge->imu->acc[2]   z-axes (up)
bridge->imu->gyro[0]  Rotation velocity around x-axes [degree/sec]
bridge->imu->gyro[1]  y-axis
bridge->imu->gyro[2]  z-axes

There is further a turn rate function (vector sum of all three gyro axes):

bridge->imu->turnrate()

There is no calculated nor calibrated scale not offset on the accelerometer reading.

The gyro offset can be calibrated using the REGBOT GUI (IMU tab).

IR-dist

There are two IR sharp sensors type GP2Y0A21, a 10-80cm sensor.

The raw response from the sensor is approximate as shown here

The part from about 8-10cm is converted to a distance in meter using the calibration points in the REGBOT GUI.

A data example is shown above in the logfiles section.

The data is accessible using

bridge->irdist->dist[0]  is distance sensor 1 [m]
bridge->irdist->dist[1]  is distance sensor 2 [m]

Pose

The robot pose includes position, orientation and tilt and is accessed as

bridge->pose->x      distance in x-direction (forward) sinse start of mission.
bridge->pose->y      y-distance
bridge->pose->h      heading in radians, zero is aligned with x-axes, positive is counter clockwise 
bridge->pose->tilt   tilt is rotation angle around the y-axis (used for REGBOT balance) (using a complementary filter (acc and gyro).
bridge->pose->dist   distance driven since start of mission [m].

The data from the same mission as above looks like.

The first plot shows that the robot moves 0.6m forward (y=0 and h=0) starting at 6 seconds and stops at 10 seconds - to take an image. After this, it takes a number of turns (about 20 degrees with a turning radius of about 0.2m) with a stop for about a second (looking for an ArUco code in the image).

After 18 seconds and the heading is about 0.9 radians, and an ArUco-code is visible. Thien the robot advances to the position of the code (in a turn-drive-turn manoeuver).

The second plot shows the position of the robot. First about 0.6m forward, then turning in small steps until the marker is seen, from there on a turn with a smaller turn radius, a straight part and a final turn to face the marker.

Calibration of the odometry is the wheel-base (distance between driving wheels) and the wheel radius. These setting must be inserted in the REGBOT GUI (robot tab).

Joy

The joystick data is available from the bridge.

The following data is available

bridge->joy->axes[0]  (left hand left-right axes)
...
bridge->joy->axis[7]  (digital up-down axes)

For the other axes see Robobot_bridge#Gamepad. The value is a signed 16-bit value (-32767 to 32766) for the axes.

bridge->joy->button[0]    Green button
...
bridge->joy->button[10]   Right knob

For the other buttons see Robobot_bridge#Gamepad. The value is 0 (not pressed) and 1 (pressed).

There is further a flag for manual override by the gamepad

bridge->joy->manual

With true or false value (true means gamepad control)

The mission from the other plots gets started with a press on the green button about 4 seconds after the start of the mission application. (the robot then further awaits the distance of IR sensor 2 is below 0.3m before starting to move).

Motor

The motor interface gives the (estimated) velocity of the two driving wheels.

bridge->motor->velocity[0]     Velocity of the left wheel in m/s
bridge->motor->velocity[1]     Velocity of right wheel

There is further access to the motor current.

bridge->motor->current[0]     Current of the left motor in Amps
bridge->motor->current[1]     Current of right motor

An example from the mission used earlier is shown. The left plot shows the estimated velocity, where the velocity starts after 6 seconds at about 0.2 m/s and going back to zero at about 10 seconds, and after that starts turning at 10.5 and 12 seconds - the right wheel drives faster. It is visible that there is significant noise on the velocity estimate.

The right current plot shows that the control is active (but not moving) with a current about 100mA. After 6 seconds there is a current peak to about 600mA that starts the motors and then drives with a current of about 250mA. Again after 10.5 and 12 seconds, there is a start-current peak.

Info

The info block holds some static data, but also data from the heartbeat message - the only part that can be logged).

From heartbeat message

 bridge->info->regbotTime           Time from REGBOT in seconds since "start" message
 bridge->info->batteryVoltage       In Volts
 bridge->info->missionLineNum       Line number in thread (the last linenumber started)
 bridge->info->missionThread        The thread number (where the line number is valid)

Basic robot info that is updated at least once at the start of the mission

 bridge->info->robotId              The REGBOT robot ID number (decides the name)
 bridge->info->odoWheelBase         The (calibrated) distance between the driving wheels (reproted by REGBOT),
 bridge->info->gear                 The gear ratio (reported by REGBOT)
 bridge->info->pulsPerRev           The number of ticks in one motor rotation (reported from REGBOT)
 bridge->info->odoWheelRadius[0]    The radius of left wheel in meters (reported from REGBOT)
 bridge->info->odoWheelRadius[1]    The radius of right wheel in meters
 bridge->info->robotname            A C-string with the robot name
 bridge->info->msgCnt1sec           Number of messages received from bridge in one second.

There is further a function that reports if communication with the robot is OK.

 bridge->info->isHeartbeatOK()      

Returns true if a heartbeat message is reported within the last 2 seconds. It should be reported about every 0.5 seconds.

Event

Holds all 34 event flags.

To test if an event has occurred use this function

bridge->event->isEventSet(X);        Where X is the event number (between 0 and 33)

This call to isEventSet(x) also clears the event flag, so that the flag is ready to be set again. And thus can be used to clear the event.

The raw event flag can be accessed in the event array:

bridge->event->eventFlags[X];     Where X is a number from 0 to 33.

Two flags have a special meaning: Event 0 stops the mission in REGBOT (and terminates the mission app). To trigger a stop event use the call:

bridge->stop();

To start a mission send the command "start" to the robot:

bridge->send("start\n");

This will trigger an event 33.

Events 30 and 31 are used in the mission app to swap between the two buffer threads and should not be used for anything else.

Events 1 to 29 can be used in mission lines to track progress.

The logfile has a list of when each of them has been set or cleared.

This plot shows the events related to the mission also used above. The first event is 31 at about 5 seconds, this will activate the first thread with drive mission lines. When the drive has reached the last line is sends an event 1 (about 9.5 seconds), this event is regularly tested by the mission app and is cleared almost immediately. It triggers a pause where an image is taken and analyzed.

After a second, the conclusion is clear and new mission lines (called a mission snipped) are sent to the REGBOT and activated with an event 30 (to the REGBOT). When the snippet is finished an event 2 is sent (from the REGBOT). This again triggers new actions in the mission app.

Edge

The edge sensor (also called line sensor) is primarily used by the REGBOT when driving on a line, but some information is available from the edge sensor:

 bridge->edge->edgeValidLeft
 bridge->edge->edgeValidRight
 bridge->edge->edgeCrossingBlack
 bridge->edge->edgeCrossingWhite

These (bool variables) will be set (to 1 (true) or 0 (false)) as detected by the line sensor but is updated at a rather slow pace (30-50ms). it is thus likely that a crossing line can be missed (the detection on REGBOT is tested evert 1ms).

'EdgeCrossingBlack' crossing a black line is never really tested, and should not be considered usable. The two variables 'edgeValidLeft' and 'edgeValidRight' are always true and false at the same time (a legacy feature).

Camera

The camera interface sets the camera to 1280 x 960 pixels at 30 frames per second.

...

ArUco

This part of the camera system is configured to detect ArUco codes with their position relative to the robot. The position is in (x, y, z), where x is forward, y is left and z is up. The reference position is the center between the driving wheels at ground level.

Mission

The mission block has access to all the other elements and controls the performance of the robot.

The mission used in the plots above is used as an example to explain how a mission is coded.

The mission is divided into segments, in this example, the code is divided into two segments called

mission1(state)    

- with the first movement (0.6m at a velocity of 0.2m/s) and is using a gamepad button, event, sound and display on the o-led display.

mission2(state)    

- that wait for the robot to stand still, take an image and do ArUco code analysis. Depending on the code analysis either the robot turns or moves to face the marker. It is using a library to calculate a manoeuvre (a turn, a straight part and an end turn to get to the destination.

The mission code is described here in a bit more detail.

Installation

Get software

Get the ROBOBOT software from the svn repository:

svn checkout svn://repos.gbar.dtu.dk/jcan/regbot/mission mission

or just update if there already

svn up

Compile

To be able to compile the demo software CMAKE needs also to use the user installed library (raspicam installed above), so add the following line to ~/.bashrc:

export CMAKE_PREFIX_PATH=/usr/local/lib

Then build Makefiles and compile:

cd ~/mission
mkdir -p build
cd build
cmake ..
make -j3

Then test-run the application:

./mission

It should print that the camera is open and the bridge is connected to the REGBOT hardware.

Sound

The robot has small speakers

Speak

system("espeak \"bettina reached point 3\" -ven+f4 -a30 -s130");

This line makes the robot say "bettina reached point 3" the parameters "-a30" turns amplitude down to 30%, "-ven+f4" sets language to english with female voice 4 and "-s130" makes the speech a little slower and easier to understand. It requires that espeak is installed (sudo apt install espeak).

To use on Raspberry pi, it is better to use

system("espeak \"Mission paused.\" -ven+f4 -s130 -a60 2>/dev/null &");

The "2>/dev/null" tell that error messages should be dumped, and the final "&" say that it should run in the background (not to pause the mission).

AruCo Marker

The camera class contains some functions to detect Aruco markers. It it described in more details on AruCo Markers.

Software documentation (doxygen)

Figure: generated with doxygen http://aut.elektro.dtu.dk/robobot/doc/html/classes.html

The classes that inherit from UData are classes that makes data available for the mission, e.g. joystick buttons (in UJoy) event flags (in UEvent) or IR distance data (in UIRdist).

The classes that inherit from URun has a thread running to receive data from an external source, e.g. UBridge that handles communication with the ROBOBOT_BRIDGE.

The camera class (UCamera) is intended to do the image processing.

HTML documentation - Doxygen

To generate doxygen html files go to mission directory and run doxygen.

cd ~/mission
doxygen Doxyfile

then open the index.html with a browser.

If doxygen is not installed, then install using

sudo apt install doxygen